Question

我想知道是否可以将执行的查询结果转换为模型列表。

我正在使用Ruby和ActiveRecord，需要执行自定义SQL查询来连接两个或多个表。代码如下所示：

connection = ActiveRecord::Base.connection
sql = "select T1.f1, T2.f2 from T1 left join T2 on T1.id = T2.id"
@result = connection.execute(sql)

在Ruby代码中，我定义了一个模型来管理执行的SQL结果：

class Model
  property :f1, :f2
end

有没有办法将@result转换为Model对象列表？所以我可以处理列表中的每个项目，如下所示

@result.each do |item|
  puts item.f1
  puts item.f2
end

Answer 1

让您的模型继承ActiveRecord :: Base

class Model < ActiveRecord::Base
end

然后你就可以这样做了

connection = ActiveRecord::Base.connection
sql = "select T1.f1, T2.f2 from T1 left join T2 on T1.id = T2.id"
@result = Model.find_by_sql(sql)

puts @result.f1

Answer 2

我现在所做的事情如下：

ActiveRecord::Base.connection_pool.with_connection do
 connection = ActiveRecord::Base.connection
 sql = "SELECT a.topic_seq, a.topic_id, a.topic_user_seq, a.topic_title, a.topic_header, t.tag_name AS topic_tag_name, to_char(a.topic_createtime::timestamp with time zone, 'Day, YYYY Mon DD'::text) AS topic_createtime FROM topics a LEFT JOIN tags t ON a.topic_tag = t.tag_seq;"
 results = connection.execute(sql)
 results.each do |row|
  obj = Model.new(row['topic_seq', row['topic_id'], row['topic_user_seq']...], 
  puts obj.topic_seq
  puts obj.topic_id
  ...
 end
end

我只是想知道是否有另一种方法可以更轻松地将行转换为Model对象而不是使用Model构造函数？

Answer 3

创建一个名为示例“ GenericObject”的通用模型：

 class GenericObject < ActiveRecord::Base    
 end

执行sql并设置table_name：

sql = "select T1.f1, T2.f2 from T1 left join T2 on T1.id = T2.id"
go = GenericObject
go.table_name = "T1" #set this for do not show message "doesn't exist: SHOW FULL FIELDS FROM"
result = go.find_by_sql(sql)

获得结果：

p result
# [{"f1": 1, "f2": "x"}, {"f1": 2, "f2": "y"}]
p result.first.f1
# 1

将执行的SQL结果转换为Model对象列表

3 个答案: